LiFePO4 (LFP) coating and blending on Li1.05(Ni0.88Co0.08Mn0.04)O2 (Ni-rich NCM): A strategy for reduced gas generation

초록

This study investigates the safety challenges associated with Ni-rich NCM cathode materials, which are critical for achieving high-energy-density lithium-ion batteries in the electric vehicle (EV) market. Despite their high capacity, Ni-rich NCM materials face significant issues related to gas generation during charging and discharging cycles, leading to safety concerns and performance degradation. To address this, LiFePO4 (LFP), known for its excellent thermal stability and low gas generation despite its lower energy density, was explored as a complementary material. In this work, Ni-rich NCM and LFP were physically blended in various ratios or coated with LFP, aiming to mitigate gas generation while preserving the high energy density of the cathode. Electrochemical tests revealed that blending and coating approaches not only enhanced the structural and electrochemical stability of the cathode but also significantly reduced gas generation during cycling. Specifically, gas evolution was reduced by over 50 % compared to pristine Ni-rich NCM cathodes, with notable decreases in CH4 and CO2 as identified by gas composition analysis. Furthermore, pouch cell tests confirmed that the introduction of LFP improved cycle retention, stabilized operating voltages, and reduced oxygen release from the cathode during high-voltage cycling. These findings underscore the effectiveness of combining Ni-rich NCM with LFP to address key safety concerns, enhancing both the thermal and electrochemical stability of the system. The proposed strategy demonstrates the potential for developing high-energy, high-safety lithium-ion batteries, providing a promising pathway for the next generation of EV batteries.

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